I continued studies on plasmid transfer and expression in Streptococcus sanguis cells. I did a clonal analysis of transformed cells to determine the fate of the newly acquired plasmid DNAs. Certain plasmids appeared to enter cells with little or no modifications. These were derived from Streptococcus pyogenes, strain SM60 containing the ERL1 plasmid. Others were changed physically, for example, pAM beta 1 derived from either Streptococcus faecalis, strains DS5 or JH2-2 pAM beta 1, or from S. sanguis, strain G102 beta. The changes observed were deletions in, or additions to, the initial molecular sizes. For example, transformed cultures contained a minimum of 18 molecular weight classes that covered the range from about 4 x 10 to the 6 to 33 x 10 to the 6. The events that lead to these changes are not understood.